A bovine papillomavirus-1 based vector restores the function of the low-density lipoprotein receptor in the receptor-deficient CHO-ldlA7 cell line

The introduced vector p3.7LDL produced functionally active LDL receptors in the receptor-deficient cell line CHO-ldlA7 during the 32-week period of observation as determined by the internalisation assay with the labelled LDL particles.Bovine papillomavirus type-1 (BPV-1)-derived vectors could be suitable for gene therapy due to their episomal maintenance at intermediate to high copy number and stable, high-level expression of the gene products. The constructed BPV-1 based vector p3.7LDL produced functionally active LDL receptors in the LDLR-deficient cell line CHO-ldlA7 during the 32-week period of observation.In vivo experiments should reveal, whether 1–5% transfection efficiency obtained in the current work is sufficient to bring about detectable and clinically significant lowering of the amount of circulating LDL cholesterol particles.The low-density lipoprotein receptor (LDLR) is an integral membrane glycoprotein that specifically binds LDL particles and mediates cholesterol homeostasis through receptor-mediated endocytosis. Mutations in the LDLR gene give rise to an inherited autosomal disease familial hypercholesterolemia (FH). The incidence of the homozygous form of FH is 1:106, whereas the heterozygous form affects 1 in 500 individuals [1]. Correction of homozygous FH is possible in several ways including liver transplantation [2], LDL apheresis [3] and plasmapheresis [4]. These treatments are laborious and in the case of liver transplantation contain several risks. Hepatocytes naturally express LDLR protein at a high level and thus are the most promising target for the LDLR gene transfer. Ex vivo and in vivo approaches have been used in liver-directed gene therapy. The ex vivo method was used in the first human LDLR gene therapy trial [5]. The in vivo introduction of the normal LDLR gene into receptor-deficient cells should potentially result in clinically beneficial effects using less invasive procedures. Several protocols for liver-directed gene transfer